Cæsar's Wife must be above Suspicion.
Reading edition
No doubt this proverb originated from a passage in Suetonius, which says that "the name of Pompeia, the wife of Julius Cæsar, having been mixed up with an accusation against P. Clodius, her husband divorced her; not, as he said, because he believed the charge against her, but because he would have those belonging to him as free from suspicion as from crime."